Table 6.

Applied hardware parameters.

Parameter	Description	Value
Vclrc	Amount of charge that will be accumulated on the capacitor C1 (Schemmel et al., 2006) in case of causal spike time correlations, corresponds to x(Δt)	0.90 V
Vclra	See Vclrc, but for the anti-causal circuit	0.94 V
Vctlow	Lower spike pair accumulation threshold	0.85 V
Vcthigh	Higher spike pair accumulation threshold	1.0 V
Adjdel	Adjustable delay between the pre- and postsynaptic spike	2.5 μA
Vm	Parameter to stretch the STDP time constant τSTDP	0.0 V
Ibcorreadb	Bias current that influences timing issues during read outs	2.0 μA
drvIrise	Rise time of synaptic conductance	1.0 V
drvIfall	Fall time of synaptic conductance	1.0 V
Vstart	Start value of synaptic conductance, need for small rise times	0.25 V
drvIout	Maximum value of synaptic conductance, corresponds to gmax	Variable

The difference V_cthigh − V_ctlow corresponds to the threshold a_th. All data is recorded with the FACETS chip-based hardware system using chip number 444 and synapse column 4.